It is well known to mix music tracks together manually, and for DJs to create mixes using music tracks stored on computers or retrieved from the Internet. In the last few years, mixing technologies have been developed to handle streamed music files. For example the App Pacemaker® has been integrated with the music streaming service Spotify®.
Properties characterizing a good music mix include primarily that the mix produces a continuous stream of music where the beat and the energy of the output are perceived as close to a continuous flow as possible. There should be a rhythm, or a pulse, that is perceived as steady and without disruptions. Any changes should be gradual, and the intensity and the dynamic should also be perceived as a continuous flow.
Creating a good mix requires knowledge of the music tracks available, and practice in handling the controls of the DJ equipment used. However, even people who lack this knowledge and experience might want to create mixes to suit their musical preferences. This involves both selecting good music tracks to mix, mixing them together and applying effects to the music tracks while they are being played back. For example, when a DJ mixes two music tracks, the playback speed of one or both music tracks may be adjusted at least for a period of time, so that the beats of the two music tracks will be in sync during the transition from the current music track to the next.
GB2370405 discloses a semi-automatic method of mixing music tracks. Two selected music tracks may be mixed together. In order to enable the mixing of music tracks, each music track that is made available is analysed and annotated manually. For each music track, crossfade sections comprising a first section at the beginning and a second section at the end of the track is specified. The first section is the part of the music track that should be mixed together with the music track immediately preceding it in the mix. The second section is the part of the music track that should be mixed together with the music track immediately succeeding it in the mix, that is, with a first section of the succeeding music track. GB2370405 only describes mixing in terms of crossfading selected music tracks in and out, and only in dependence of crossfade sections that must be specified manually in advance.
US Patent publication No. 2008/0249644 A1 discloses a method for automatic mixing of music tracks. The method is based on determining a property such as the timbre of each music track and then select two music tracks that are as similar as possible, to be mixed together. This does not always yield a satisfactory result for the listener.
There are other DJ programs, such as DJAY, that will mix files by automatically crossfading but without performing any analysis or adaptation of the files. This means that mix parameters, such as the amount of overlap between music tracks, must be set manually by the user.